This application relates generally to steering columns, and more particularly to adaptive energy absorbing devices for collapsible steering columns.
Automotive steering column assemblies are often equipped with kinetic energy absorbing devices to reduce the likelihood of injury to an operator in the event of collision. One such device employs a plastically deformable metal strap which is drawn across an anvil in a crash event during the collapse of the steering column to absorb some of the energy of collapse.
Typically, the anvil is fixed and thus there is little control over the performance of the absorbing device.
An energy absorbing device for a collapsible steering column of a vehicle comprises a housing having at least one fixed abutment surface. At least one adjuster having an initial abutment surface is disposed in the housing for selective laterally slidable movement therein. At least one anvil is disposed in the housing between a surface of the housing and the initial abutment surface of the adjuster defining a first position of the anvil. A plastically deformable strap is supported at least in part between the anvil and the housing. The anvil has an arcuate mating surface engaging the strap restricting slidable movement therebetween. A base portion of the anvil engages the initial abutment surface of the adjuster maintaining the base portion in spaced relation from the fixed abutment surface of the housing. The adjuster is laterally slidable in response to a signal in a crash condition of the vehicle removing the adjuster from between the anvil and the housing. The base portion of the anvil can then move from the first position into mating contact with the fixed abutment surface of the housing in response to an applied force from the strap defining a second position of the anvil. The arcuate surface of the anvil has a first coefficient of friction against the strap while the anvil is in the first position and a second coefficient of friction against the strap while the anvil is in the second position. The second coefficient of friction is less than the first coefficient of friction, thereby allowing the steering column to collapse under a lighter axial load while the anvil is in the second position.
One object of the invention is to provide an energy absorbing device for a collapsible steering column that compensates for the severity of a vehicle crash and the size, weight and/or position of the driver.
The invention has the advantage of providing selectively slidable anvils which can move between different positions to vary the reaction path of the strap, and thereby control the energy absorption characteristics of the system.
One further advantage is that the system is of simple construction and is adaptable to many different crash conditions.
Other objects, features and advantages of the invention will become more apparent in view of the following description and drawings.